linux-kernel - Re: [PATCH v4 7/7] dma-buf: system_heap: Add a system-uncached heap re-using the system heap

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Date:   Thu, 29 Oct 2020 15:28:34 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     Hillf Danton <hdanton@...a.com>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Liam Mark <lmark@...eaurora.org>,
        Robin Murphy <robin.murphy@....com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Simon Ser <contact@...rsion.fr>,
        Christoph Hellwig <hch@...radead.org>,
        James Jones <jajones@...dia.com>,
        linux-media <linux-media@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v4 7/7] dma-buf: system_heap: Add a system-uncached heap
 re-using the system heap

On Thu, Oct 29, 2020 at 12:10 AM Hillf Danton <hdanton@...a.com> wrote:
> On Thu, 29 Oct 2020 00:16:24 +0000 John Stultz wrote:
> > @@ -194,6 +210,9 @@ static int system_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
> >       struct sg_page_iter piter;
> >       int ret;
> >
> > +     if (buffer->uncached)
> > +             vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
> > +
>
> Wonder why you turn back to dma_mmap_wc() and friends?

Sorry, can you expand on what you are proposing here instead?  I'm not
sure I see how dma_alloc/mmap/*_wc() quite fits here.

thanks
-john